A shocking one quarter of all shark and ray species are threatened with extinction, according to the results of a new study.

The great white shark is classified as Vulnerable on the IUCN Red List

Threat analysis

The paper, published this week in the open-access journal eLife, analysed the threat and conservation status of an impressive 1,041 species of chondrichthyans, a fascinating group of fish species including sharks, rays, skates and chimaeras whose skeletons are made of cartilage rather than bone. The results were rather alarming, revealing that this group is among the most threatened in the animal kingdom.

The paper is the result of collaboration between more than 300 experts from 64 countries, and reports that, while no species has yet been driven to global extinction, at least 28 populations of skates, sawfishes and angel sharks are now locally or regionally extinct. In addition, several shark species have not been seen for several decades.

Reef manta ray parts are highly valued in traditional medicine, posing a threat to this majestic species

Threat hotspots

The study highlights two areas which are currently experiencing a higher than expected level of threat: the Red Sea and the Indo-Pacific Biodiversity Triangle. The latter is considered to be among the most biologically and culturally diverse regions on the planet, yet unfortunately it is also one of the least regulated.

The authors of the paper explain that, “The Indo-Pacific Biodiversity Triangle, particularly the Gulf of Thailand, and the islands of Sumatra, Java, Borneo, and Sulawesi, is a hotspot of greatest residual threat, especially for coastal sharks and rays with 76 threatened species.”

It is feared that, should no national or international action be taken, these species could rapidly become extinct.

Finning was revealed to be a major threat to many shark species

Major threats

The results of the study revealed that the main threat to chondrichthyans is overexploitation through targeted fisheries and incidental catches. Of particular concern for the future of sharks, wedgefishes and sawfishes is the process of ‘finning’, which is driven by the huge market demand for shark fin soup, a highly sought-after delicacy in China.

The authors of the new research paper state that, “Fins, in particular, have become one of the most valuable seafood commodities. It is estimated that the fins of between 26 and 73 million individuals, worth US$400-550 million, are traded each year.”

Habitat loss is a further threat to chondrichthyans, with 22 species being threatened by the destruction of estuaries and river systems for the purposes of residential and commercial development, and 12 species being placed at risk due to the conversion of mangroves into shrimp farms. In addition, pollution and climate change have been identified as major threats to sharks, rays and their relatives.

The scalloped hammerhead shark is classified as Endangered on the IUCN Red List

Additional factors

As well as providing a vital insight into the type and extent of threats to chondrichthyans, the paper also revealed other interesting factors which come into play. It was found that large body size and occurrence in shallow habitat are the biggest factors determining a species’ likelihood of being threatened. The results showed that with every 10-centimetre increase in a species’ maximum body length came a 1.2-percent increase in the probability that the species would be threatened. Dwellers of deep water appear to fare better than their shallow-water relatives, with a 10.3-percent decrease in the probability of being threatened for every 50-metre increase in the minimum depth limit of the species.

The observance of Thanksgiving Day is primarily associated with the United States, and is a tradition which is thought to date back to colonial times following the safe arrival of the first European settlers to the untamed shores of North America. Nowadays, families and friends congregate to give thanks for what they have, so to celebrate Thanksgiving in our own wild way, we’ve gathered together a few of nature’s special inhabitants that we think owe each other thanks: symbiotic species!

Exclusive residence

Common clownfish are able to live among the tentacles of stinging sea anemones

Simply speaking, symbiotic species are those that interact in some way, to the benefit of one or both of the critters in question. A classic example, and one that many Disney fans will be familiar with, is the relationship that exists between clownfish and sea anemones.

Sea anemones usually sting fish that come into contact with their tentacles, but clownfish have developed a clever, yet rather gross, method of disguise. By covering its skin in mucus, the clownfish can trick the anemone into thinking it is touching itself, and so does not get stung. In return for a safe place to live and food in the form of debris and parasites found amongst the anemone’s tentacles, the clownfish is thought to scare away fish that may prey upon the anemone, and even lure fish in for its tentacled home to eat – a classic win-win situation! The clownfish is also believed to provide the anemone with good water circulation through fanning its fins as it swims around.

Did you know?

There are different kinds of symbiotic relationships. Some benefit both species involved, and are known as ‘mutualistic’ symbioses, whereas ‘parasitic’ relationships are those in which one species profits at the expense of the other. In some cases, one species benefits but the other is affected neither positively nor negatively, and these are known as ‘commensalistic’ symbioses.

Nutritious nectar and pollen parcels

Bees, such as this small garden bumblebee, play an important role in plant pollination

Bees feed on pollen and nectar sourced from a variety of flowering plants, with honey bees using the nectar to make their sticky, sugary treat. Although flowers appear to lose out by ‘donating’ nectar, they actually benefit from these flying visits. As a bee rummages around the flower head for food, some pollen gets stuck to its hairy body and legs, and this accidental cargo is then transferred to the next flower the insect visits, pollinating it and enabling the plant to reproduce.

Did you know?

The traditional origin of the modern Thanksgiving Day is commonly thought to be the festivities that occurred at the Plymouth Plantation in Massachusetts in 1621, when the European settlers celebrated their safe voyage, peace and good harvest. However, there is some evidence to suggest that Spaniards in Florida were the first to truly celebrate Thanksgiving back in 1565.

Getting a little peckish…

Oxpeckers help remove parasites from large mammals such as this roan antelope

In the wilds of the African savanna, large mammals such as this roan antelope can quickly become covered in ticks and all sorts of other creepy crawlies, which doesn’t sound entirely pleasant! Luckily, help is at hand in the form of winged wonders known as oxpeckers. Oxpeckers are known to hitch a ride on the backs of a range of iconic species including hippos, buffalos, giraffe and various antelopes, gorging themselves on ticks, botfly larvae and other parasites – the mammals get cleaned, and the birds get fed, and so this has often been classified as a mutualistic relationship. However, more recent studies have shown that oxpeckers often pick at scabs and cuts to keep them open to get more food, subjecting the wounds to possible infection and potentially harming the host mammal, making this symbiotic relationship more of a parasitic one.

Helpful houseguests

Reef-building corals rely on tiny blue-green algae to survive

Reef-building corals provide homes for single-celled blue-green algae known as zooxanthellae, and in return these microscopic plants provide energy-containing compounds for the coral through the process of photosynthesis. The coral uses these vital compounds to build its calcium carbonate skeleton. In a way, these tiny blue-green algae are like live-in coral chefs…and they even clean up after themselves by removing any waste products! Brilliant!

Nature’s six-legged gardeners

Leaf-cutter ants tend to their fungus garden by creating ‘mulch’ from leaf fragments

Leaf-cutter ants are known as nature’s gardeners, as they spend their time foraging for leaves and cutting them into suitably sized fragments before transporting them back to their huge underground nests where the leaves are used to cultivate a fungus garden. While the ant colony is entirely dependent upon this fungus supply for food and so greatly benefits from this situation, the fungus benefits by being cultivated by the ants but also loses out by being eaten, and so this relationship could be classified as a more commensalistic one.

Did you know?

Most of us think of the US in relation to Thanksgiving, but did you know that several other countries observe similar days, too? These include Canada, Puerto Rico and Liberia. Additionally, the city of Leiden in South Holland celebrates the traditional US Thanksgiving Day, making the Netherlands the only non English-speaking country to formally celebrate this particular occasion.

Food on the go…

Dugong

Loggerhead turtle

Leopard shark

Giant manta ray

Scientists are somewhat divided over whether the relationship that exists between specialised fish known as remoras and a variety of larger ocean species is a mutualistic or commensalistic one. Also known as suckerfish, remoras have a specially adapted first dorsal fin which has been modified into a sucker-like organ. Remoras use this to attach themselves to other marine animals such as sharks, rays, sea turtles and dugongs, feeding on material dropped by the host species while also getting a free ride and protection from potential predators. This seems rather one-sided, but some scientists believe that the remoras may also feed upon certain parasites on the host’s body or gills, therefore providing a great cleaning service to their marine meal providers.

If these beholden bovids, indebted invertebrates and contented chondrichthyans haven’t quenched your thirst for wild Thanksgiving-related information, why not check out last year’s blog, which features a whole host of awesome animals that the first European settlers might have seen upon arriving in North America.

As Shark Week continues to float on here in the US, we think it’s the perfect time to shine the spotlight on some of the strangest-looking sharks found on Earth. We all know what the great white shark looks like but have you seen a shark with an ‘executioner’ style hood over its head or one with a beard? Read on to see how many of these bizarre sharks are new to you!

10. Trendy trim

With a chic patterning of splotches over its body, the leopard shark roams the ocean in the day and night. Despite the fear that all sharks are dangerous, the leopard shark is actually harmless to man and even approachable when it lounges on the sea floor during the day.

9. An immense encounter

We think this shark merits an appearance on this list just for its sheer size. The largest fish in the sea, the whale shark can weigh up to 13 tons. Perhaps ironically, the biggest fish in the world feeds primarily on some of the smallest organisms, tiny planktonic organisms.

8. Hard-headed

The blunt snout of this species along with its large eyes makes the kitefin shark a perfect addition to our list. The kitefin shark is uniquely ovoviviparous meaning it gives birth to live young instead of laying eggs like most other fish species.

7. Hooded hider

With a black mask over its head and snout, the hooded carpet shark is said to resemble an eerie ‘executioner’s hood’. The addition of white spots that cover most of its body helps this species to blend into surrounding coral until this nocturnal shark comes to life at night.

6. Wide-eyed wonder

Check out the blinders on this fish! The crocodile shark is a small slender shark known for its short head and large eyes likely used to hunt effectively at night. Following its prey towards the water surface at night and away during the day, the crocodile shark is an active hunter which enjoys a wide variety of prey including squid, fish, and shrimp.

5. See a saw

Aptly named, the green sawfish has an elongated snout with over 23 pairs of teeth. By using this impeccable nozzle, the green sawfish is able to feed on slow-moving fish by clubbing at them with a side of its saw. Cleverly, the green sawfish uses its saw to act as a shovel-like instrument to rake out crustaceans.

4. Face of an angel

Sometimes mistaken for a large ray due to its appearance, the angel shark has a remarkably flat body and well-placed eyes on the top of its head that are perfect for ambush-style predation. The angel shark is Critically Endangered, likely due to its prevalence in by-catch – the accidental capture of species through standard fishing practices such as trawling. Sadly, this species has been declared extinct in the North Sea.

3. Mega mouth

As the second largest fish in the sea, the basking shark is one to impress. Perhaps a good kisser, the basking shark uses its three-foot-wide mouth to filter feed while it ‘basks’. Not too interested in the social scene, the solitary basking shark is thought to hibernate in deep water.

2. Ancient allure

The frilled shark is one of the most primitive species of living shark. Having perfected its look to have a lizard-like, blunt-ended snout and a very large mouth, the frilled shark possesses an unconventional beauty. Living primarily in the deep-water darkness, this three-foot-long and mysterious beast has had few observations made in its natural environment.

1. Camouflaged charmer

Literally meaning ‘well fringed nose with shaggy beard’, the tasselled wobbegong is an exceedingly unusual looking shark. With its branching skin flaps and a lofty lattice-like ‘beard’ the wobbegong’s bristles provide it with a sagacious camouflage and overall appearance. We challenge you to find a weirder-looking shark on ARKive!

Were any sharks on our list new to you? Or do you have a favorite to add to the list? Surf the ARKive site for more sharks and share your favorites in the comments below!

As most of people don’t have enough spare time to watch the 8,522 videos currently on ARKive (although you may wish you did), we thought we’d give you a helping hand by choosing what we considered to be the top ten videos of one of the world’s most endearing animals: the shark. After perusing all of the magnificent shark footage on ARKive we managed to whittle them down to just ten terrifying, awe-inspiring and bizarre videos.

Gentle giants

The whale shark is the biggest fish in the world, measuring as much as twelve metres and weighing up to 12,500 kilograms. It is a fairly docile species and feeds mostly on plankton and small fish, actively sucking in prey through its large mouth. Its sheer size can be acknowledged when compared with the diver in this video:

It’s fin may cut the surface of the water in a way which could instil fear into the most courageous humans, but the basking shark is more interested in devouring microscopic prey. The basking shark is the second largest fish in the world and has a mouth that can measure up to a metre across when fully open. See it feeding in this fascinating footage:

Out of the ordinary

The mysterious megamouth shark was only described as recently as 1976 and is so genetically different from other sharks that it was placed in its own family. It can reach over five metres in length and its oversized mouth has over 50 rows of tiny, hooked teeth. See this strange species in action in this video:

Friends with benefits

The Greenland shark is one of the largest sharks in the world, measuring up to seven metres. Almost all Greenland sharks are parasitized by a minute crustacean which attaches itself to the shark’s cornea and gradually destroys the host’s eyesight. It is thought to be a mutually beneficial relationship as the crustacean may act as a lure for fish, although this is unconfirmed. See it in action here:

The strange-looking scalloped hammerhead has a mutually beneficial relationship with cleaner wrasse. This helpful fish eats parasites from the skin and mouth of the scalloped hammerhead shark, as well as cleaning any wounds, as shown in this video:

Remarkable reproduction

Most sharks are ovoviviparous, with the young developing within eggs in the body of the female. The eggs then hatch inside the female, who then gives birth to the well-developed young. However, the lemon shark, similarly to humans, is viviparous and the young develop inside the female, while receiving nutrients from an internal placenta and the female then gives birth to live young. See this extraordinary event unfold here:

Expensive taste

The salmon shark, as its name suggests is thought to be one of the main predators of Pacific salmon. It is similar in appearance to the great white shark and shares its excellent predatory skills. The salmon shark may have the highest body temperature of any shark, which allows them to maintain warm muscles and organs, so they are still able to hunt in the ice cold waters of the North Pacific Ocean. See this giant in its habitat here:

Quick off the mark

The shortfin mako is thought to be the fastest shark species and is capable of reaching speeds of up to 35 kilometres per hour. Its high tail and efficient heat exchange system enable it to quickly pursue its prey, as shown in this video:

Fearsome fish

No list about sharks would be complete without mentioning the formidable great white shark. A tremendously skilled predator, it is at the top of the marine food chain and is known to hunt fish, turtles, molluscs, dolphins, porpoises and seals. Their powerful bodies enable them to leap from the water in pursuit of prey, as shown in this video:

Fighting back

The tiger shark is one of the largest shark species and is known for its voracious appetite, eating anything from fish to car license plates. Although the inanimate objects it predates on are unlikely to fight back, its more alive prey may create more problems, much like the loggerhead turtle in this video:

The UK has been experiencing some uncharacteristically hot weather over the last few weeks, so what better time to get out to our beautiful coast? Take this opportunity to find out more about the fantastic diversity of species and habitats we have off our shores, and join in The Wildlife Trusts’ annual National Marine Week! This celebration of all things marine actually runs for more than two weeks, from Saturday 27 July to Sunday 11 August, to make the most of the tides.

Velvet swimming crab

We are fortunate in the UK to have an awe-inspiring range of habitats and species around our coasts. From shallow seagrass meadows and kelp forests to gullies and canyons over 2,000 metres deep, these habitats provide homes and feeding grounds for countless species, including colourful sea slugs, charismatic fish such as the tompot blenny, and the bottlenose dolphin, one of 11 species of whale, dolphin and porpoise regularly seen in our waters! Our seas are also home to the second largest fish in the world, the basking shark. This gentle giant can be spotted in the summer as it comes close to the shore, filter feeding micro-organisms.

Basking shark

All around our coasts, Wildlife Trusts staff and volunteers will be sharing their knowledge, so whether you want to find out more about minke whales or molluscs, velvet swimming crabs or strawberry anemones, breadcrumb sponges or butterfish, and seals or seabirds, there will be events where people can enjoy the sights, sounds and smells of the sea and learn more about its riches.

The Wildlife Trusts hold these events to showcase some of the UK’s marine wildlife, and to educate and enthuse people about this fantastic resource on our doorstep. As well as being a source of wonder, our seas are also a playground, a food supply, a conduit for our imports and exports, and a climate regulator that absorbs vast quantities of greenhouse gases while releasing the oxygen we breathe. We are an island nation, and the sea is a vital part of our national identity.

Jewel anemones

However, the seas are not as productive as they once were. For years, we have taken too much with too little care. Our seas’ resources are not inexhaustible, and their ability to cope with the pressures we put on them – damage from fishing, industrial pollution and the impacts of a changing climate – is limited. Much of our marine wildlife is in decline. Two species of whale and dolphin have become extinct in UK waters in the last 400 years, and basking shark numbers have declined by 95%. Commercial species are also under pressure, and in 2009 the EU Commission declared that 88% of marine fish stocks were overexploited.

Grey seal

In order to provide better protection for our marine environment, here at The Wildlife Trusts we are campaigning for an ecologically coherent network of Marine Protected Areas – areas that offer protection not just to our most rare and vulnerable species, but to the full range of species and habitats found in the seas.

These areas will protect marine life within their boundaries, and with careful management they can also have an influence beyond these boundaries, as burgeoning populations spill out into the surrounding sea. A well-designed and effectively managed network will help boost the health of the marine environment as a whole, helping it to recover from past impacts and sustain current pressures. Although we have made a start on our network, we still have a long way to go, and at the moment progress towards achieving the network is slow.

The Wildlife Trusts’ National Marine Week and our events provide us with a crucial opportunity to highlight the need to continue to put pressure on UK Governments to ensure that this vital ambition is achieved. It offers countless opportunities for people to savour the seaside and find out so much more about what our coasts have to offer. Why not head over to The Wildlife Trusts’ marine wildlife weeks page to find an event near you!